From e28ae9232e80fc6f8753dd047498b8ded0f43860 Mon Sep 17 00:00:00 2001
From: Alec Larson <1925840+aleclarson@users.noreply.github.com>
Date: Wed, 6 Nov 2024 17:10:58 -0500
Subject: [PATCH] fix: ensure `Alias#colnames` is optional

Closes #4
---
 scripts/generateTypes.ts | 17 +++++++++--------
 scripts/typeMappings.ts  |  5 +++++
 src/lib/ast.ts           |  2 +-
 3 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/scripts/generateTypes.ts b/scripts/generateTypes.ts
index df1213f..45613c8 100644
--- a/scripts/generateTypes.ts
+++ b/scripts/generateTypes.ts
@@ -1,6 +1,6 @@
 import fs from 'node:fs'
 import type { NodeFieldMetadataByTag } from './inferFieldMetadata'
-import { typeMappings } from './typeMappings'
+import { nullableFields, typeMappings } from './typeMappings'
 
 /** A record of node tag -> field name -> nullability */
 const nodeFieldsByTag: NodeFieldMetadataByTag = JSON.parse(
@@ -320,10 +320,9 @@ async function main() {
             continue
           }
 
-          let fieldType = applyTypeMapping(
-            typeName + '.' + fieldName,
-            field.c_type,
-          )
+          const fieldPath = typeName + '.' + fieldName
+
+          let fieldType = applyTypeMapping(fieldPath, field.c_type)
 
           if (fieldName === 'type' && fieldType === 'NodeTag') {
             // Strangely, the result of pg_query_parse doesn't actually include
@@ -387,9 +386,11 @@ async function main() {
             warnUnknownType(typeName + '.' + fieldName, 'list type')
           }
 
-          const nullable = fieldMetadata
-            ? fieldMetadata[fieldName]?.[0] ?? true
-            : /\b(NULL|NIL)\b/.test(field.comment ?? '')
+          const nullable =
+            (fieldMetadata
+              ? fieldMetadata[fieldName]?.[0] ?? true
+              : /\b(NULL|NIL)\b/.test(field.comment ?? '')) ||
+            nullableFields.has(fieldPath)
 
           fieldTsDef += `  ${fieldName}${nullable ? '?' : ''}: ${fieldType}\n`
         }
diff --git a/scripts/typeMappings.ts b/scripts/typeMappings.ts
index 153cf4d..e3b24cc 100644
--- a/scripts/typeMappings.ts
+++ b/scripts/typeMappings.ts
@@ -26,6 +26,11 @@ export const typeMappings: Record<string, string> = {
   'SelectStmt.valuesLists': 'List<Expr>[]',
 }
 
+/**
+ * If a field's nullability is incorrectly inferred, add it here.
+ */
+export const nullableFields = new Set(['Alias.colnames'])
+
 function Node(types: string) {
   return types
     .split(' | ')
diff --git a/src/lib/ast.ts b/src/lib/ast.ts
index 772c016..f02cb6c 100644
--- a/src/lib/ast.ts
+++ b/src/lib/ast.ts
@@ -4966,7 +4966,7 @@ export type Alias = {
   /** aliased rel name (never qualified) */
   aliasname: string
   /** optional list of column aliases */
-  colnames: { String: String }[]
+  colnames?: { String: String }[]
 }
 
 /**